WRF-ARW Model Research Articles

Lightning data assimilation in the WRF-ARW model for short-term rainfall forecasts of three severe storm cases in Italy

This study analyses the impact of total lightning data assimilation on cloud-resolving short-term (3 and 6 h) precipitation forecasts of three heavy rainfall events that occurred recently in Italy by providing an evaluation of forecast skill using statistical scores for 3-hourly thresholds against observational data from a dense rain gauge network. The experiments are performed with two initial and boundary conditions datasets as a sensitivity test. The three rainfall events have been chosen to better represent the convective regime spectrum: from a short-lived and localised thunderstorm to a long-lived and widespread event, along with a case that had elements of both.This analysis illustrates the ability of the lightning data assimilation (LDA) to notably improve the short-term rainfall forecasts with respect to control simulations without LDA. The assimilation of lightning enhances the representation of convection in the model and translates into a better spatiotemporal positioning of the storm systems. The results of the statistical scores reveal that simulations with LDA always improve the probability of detection, particularly for rainfall thresholds exceeding 40 mm/3 h. The false alarm ratio also improves but appears to be more sensitive to the model initial and boundary conditions. Overall, these results show a systematic advantage of the LDA with a 3-h forecast range over 6-h.

Numerical simulation of land and sea-breeze (LSB) circulation along the Guinean Coast of West Africa

This study uses both observed and simulated data to investigate the diurnal evolution of land and sea-breeze (LSB) circulation across the Guinean Coast of West Africa. Numerical simulations, with ERA-Interim and CFS as forcing data, were carried out using a modified WRF-ARW model code to evaluate the model’s ability to capture the LSB kinematics over West Africa. Two simulation runs were performed with each data set. Comparison of the simulated and observed winds showed that the WRF model was able to capture the rotation of LSB in the coastal areas of the region very well. Results also showed that the simulated diurnal evolutions of the hodographs and onshore/offshore winds were found to be in good agreement with the observations. Furthermore, the simulations showed complex patterns of clockwise (CR) and anti-clockwise rotations (ACR) across the Guinean Coast. The sense of rotation is a result of complex interaction between surface and synoptic pressure gradients, horizontal and vertical diffusion, and advection terms. Overall, the results of the analysis showed that the balance is not always dominated by the pressure gradient terms, as suggested by earlier studies. However, hourly analysis of the rotation terms strongly indicates that over the ocean, surface pressure gradients dominate, while diffusion terms are more important over land areas. The Coriolis term was found not to be significant, the study area being close to the equator. Significantly, regions over water are found to be dominated by ACR, while land areas showed more CR. This may be attributed to the variation of surface roughness due to the landscape and urbanization.

Sensitivity of meteorological variables on planetary boundary layer parameterization schemes in the WRF-ARW model

The accuracy of meteorological fields produced by Numerical Weather Prediction (NWP) models are highly dependent on the physical parameterization schemes used. Any errors in simulations of meteorological fields will be passed on to subsequent processes (i.e. air quality models), and will have an effect on their outputs. Therefore, the realistic simulation of meteorological parameters is of utmost importance. The aim of the present research is to evaluate the performance of Planetary Boundary Layer (PBL) schemes contained in the non-hydrostatic Advanced Research Weather Research and Forecasting (WRF-ARW) model when simulating meteorological variables. Four frequently used PBL schemes were investigated by conducting sensitivity experiments during a month in spring and winter in the South African Highveld region for 2016. The simulations resulting from the different schemes were compared against one another, and statistically evaluated by making use of observational meteorological data at five sites. From these results, it is recommended that a local scheme be used for the Highveld region during winter. During spring, the clearly preferred scheme for the Highveld is Mellor–Yamada–Janjić (MYJ) scheme. Results from this study contributes to the establishment of a preferred PBL scheme in the WRF-ARW model, for use in South African Highveld region. Future planned research will considered the effect of the above-mentioned PBL schemes in the simulation of air quality over the same region.

Sensitivity studies of cloud microphysical schemes of WRF-ARW model in the simulation of trailing stratiform squall lines over the Gangetic West Bengal region

In this paper an attempt has been made to investigate the impact of different microphysical (MP) parameterization schemes in simulation of leading convective line with trailing stratiform (TS) squall lines observed over the Gangetic West Bengal (GWB) region of India during the pre-monsoon season of March–May using Advanced Research Weather Research and Forecasting (WRF-ARW). The model is employed to study the features associated with three TS squall line (May 15, 2009, May 5, 2010 and May 7, 2010) observed over the study region. The model sensitivity is evaluated with four different microphysics schemes of the model (Goddard, WDM6, Thompson and Morrison). Model simulations are carried out with three two-way nested domains with horizontal resolution of 18, 6 and 2 km grid spacing and explicit convection in the innermost domain. The model simulated results are compared with available observations (Surface data, rainfall, hydrometeors and Doppler Weather Radar products). The analysis demonstrates that the simulation of TS squall lines are very sensitive to the parameterization of microphysical processes of different MP schemes, in spite of using similar initial and boundary conditions and model configuration. The model provides better simulations of rainfall, maximum reflectivity and vertical profiles of hydrometeors with the Morrison MP Scheme. The study reveals that snow and graupel particles has significant impacts on the simulation of stratiform precipitation region of the TS squall line. The study suggests that simulation of TS squall lines using a high-resolution mesoscale model with suitable cloud microphysics scheme is useful for the prediction of such severe events.

Study of atmosphere dynamics in the event of very heavy rain causing flood in Supadio International Airport Pontianak using WRF-ARW Model and Himawari-8 Satellite Imagery (Case study: November 11, 2017)

On November 11, 2017, extreme weather in the form of very heavy rain has occurred in Pontianak. Based on surface observations data from Supadio Meteorological Station, the amount of rainfall reached 187.4 mm / day and caused flooding in several areas in Pontianak. As a result, a number of flights were cancelled on November 12, 2017 due to flooding in the airport runway. This study aims to examine the causes of very heavy rain using the WRF-ARW model and the results of Himawari-8 satellite images which are processed using Python Programming. Based on the output of the WRF-ARW model with the resolution 3 km, it shows some weather parameters that have potential for bad weather in Pontianak, namely the existence of shear line in West Kalimantan and the eddy circulation in this region which can trigger convective cloud accumulation in Pontianak, the wet RH in the 850-500 mb layer ranges from 70-90%, the CAPE ranges from 1000-2000 J/kg, and the air pressure decreases between 03.00 UTC until 06.00 UTC with a 1.7 mb tendency. In addition, the results of the Himawari-8 Satellite Image show that the cloud peak temperature is very low at -75.8°C at 08.33 UTC. Therefore, based on the WRF-ARW and Himawari-8 Satellite results, those support the occurrence of very heavy rain in Pontianak.

Orographic and lake effect on extreme precipitation on the Iranian coast of the Caspian sea: a case study

This paper presents the results of numerical modelling of extreme precipitation on the southern coast of the Caspian sea using the WRF-ARW model with realistic and idealised conditions aimed at evaluating the orographic and lake effects. Verified against the observational data, this model reproduces the spatial distribution and the total amount of precipitation in selected episodes reasonably well, with a certain set of physical parametrizations. Sensitivity tests showed that the lake effect is evident only in the presence of orography. The total contribution of the warm Caspian sea and orography to the amount of precipitation is, on average, 50%.

Моделирование скорости ветра при низовой метели с помощью модели WRF-ARW

Моделирование скорости ветра при низовой метели с помощью модели WRF-ARW

Impacts of Anthropogenic Heat Flux and Urban Land-Use Change on Frontal Rainfall near Coastal Regions: A Case Study of a Rainstorm over the Pearl River Delta, South China

AbstractThis study investigated heavy frontal rainfall that occurred on 13–14 October 2011 over the Pearl River Delta (PRD) in China. The frontal rainstorm was simulated using the WRF-ARW Model (version 3.3), which included its urban canopy model. Although the model-simulated convection occurred 2 h early and the second precipitation peak was underestimated, the model represented the formation, development, and extinction of the frontal rainfall and captured the distribution of the peak value. In addition, the averaged value of 49.7 W m−2was taken as the anthropogenic heat flux (AHF) of the PRD, and two land-use datasets were adopted: one for 1992 and the other for 2011. The simulation revealed that AHF and urban land-use change (ULUC) increased the total rainfall over the PRD by 6.3% and 7.4% and increased the maximum hourly rainfall intensity by 24.6% and 21.2%, respectively. Furthermore, to elucidate the mechanism of AHF and ULUC influence, the rainstorm structure, low-level jet (LLJ), and CAPE of the rainfall event were analyzed. It was found that AHF and ULUC enhanced two strong southward LLJs located over the urban areas, which carried abundant water vapor to the PRD and generated additional upper-level CAPE. This not only sustained steady ascent of the air, but it also created conditions favorable for downward motion, resulting in large persistent convective clouds and heavy frontal rainfall.

Statistical characterization of vertical meteorological profiles obtained with the WRF-ARW model on the central Andes of Peru and its relationship with the occurrence of precipitation on the region

The work carried out a characterization of tropospheric vertical profiles in rainy and dry seasons by behavior of thermodynamic indices obtained with the WRF model for the period January 2018–March 2019 on the central Andes of Peru and its relationship with rainfall in the region. A case study was also analyzed using sounding observation data. The precipitation observed were taken from 8 meteorological stations located in the Mantaro basin belonging to the National Meteorological Service of Peru. As a results, it was found that the behavior of the thermodynamic parameters responds to the general characteristics of each period. The level of condensation was always higher in the dry period, in which the lower troposphere was also more stable. The KI, TT, Sweat and CAPE indices were always higher in the rainy season, as was water vapor mixing ratio. The vertical shear was mostly higher in the dry period. The parameters that were most informative to precipitation forecasting in rainy period were the precipitation predicted by the model WRF, the average relative humidity of the 600–400 hPa layer and the water vapor mixing ratio in the layer itself. The shear in the 650–500 hPa and 550–400 hPa layer was also informative for two locations. In general, the indices were not very informative for the forecast of extreme rains. For the dry season, the relationship between thermodynamic indices and rainfall was not analyzed because it is very scarce at this time of year. The case study showed that in general, the thermodynamic parameters analyzed for each day, responded to the fact of a rainy day in relation to another dry day. • The behavior of the thermodynamic parameters analyzed responds to the general characteristics of each period. • The statistical downscale or “bias correction” markedly improved the WRF precipitation forecast. • The parameters that were most repeated in the statistical equations were the WRF precipitation. • The shear in the 650–400 hPa and 550–400 hPa layer was also informative for some locations. • The indices were not informative enough to forecast extreme precipitations.

Investigation of Meteorological Conditions Favourable for Formation of Thunderstorm Occurred Over Bangladesh Through Simulation by WRF-ARW Model

Investigation of meteorological conditions favorable for formation of pre-monsoon thunderstorm over Bangladesh has been conducted by simulating a selected thunderstorm case using ARW dynamic core of WRF model (WRF-ARW). A multi-cell thunderstorm formed on 30-03-2018 over the northwestern tip of Bangladesh and adjacent territories of India and moved south-southeast wards with its highest development at 09:30 UTC was selected for this study. The chosen case of thunderstorm has 3 distinct cells of which 2 cells have the width of over 100 km each and the third one located in the eastern Bangladesh and had the width of 50 km. A WRF ARW model has been applied to examine the atmospheic characteristics favorabe for genesis of selected case run in a double nested domain of resolution of 9x9 km2 in the outer domain and 3 3 km2in the inner domain. The analysis of the geopotential height field of 925 hPa level generated by WRF model at different hours of 31 March 2018 clearly indicates favourable condition with pockets of micro lows and their progression towards central to southeastern Bangladesh. The strong winds blowing from Bay of Bengal along an anticyclone over the Bay brings sufficient moisture to the north. The southerly winds meet the easterly and also westerly winds providing strong low level convergence which favors the convective activities forming cumulus cells. The orography of foothills may also enhance the convections. The wind in the upper tropospheric winds attains jet speed over these areas. The distribution of divergence and vorticity in the 925 hPa level shows the evolution of system. The distribution of precipitation shows that the spatial patterns were well captured. Vertical velocity has been plotted along the vertical-horizontal plane oriented in the east-west direction across a high rainfall cell. This shows that the highest development of narrow vertical cell extends up to 100 hPa level. Following the temporal evolution of the system, it is seen that the highest development delayed by around 2 hours. Some mitigation strategies in respect of thunderstorms and associated lighting are also discussed.
 Dhaka Univ. J. Sci. 68(1): 71-77, 2020 (January)

Identification of atmospheric dynamic condition during heavy rainfall in Banjarnegara Indonesia using WRF-ARW model: case 18 June 2016

The Atmospheric dynamic condition during heavy rainfall on 18 June 2016 in Banjarnegara was examined using the Weather Research and Forecasting (WRF) model. This study calculated hourly atmospheric instability indices and three kind of atmospheric dynamic parameters such as vorticity, vertical velocity, and divergence. Vorticity described cyclonic movements for the cloud growth, vertical velocity described the speed of lift force, and divergence described the existence of air mass encounter in the atmosphere. The final (FNL) data and suitable schemes are applied for the nested domains (27 km, 9 km, 3 km) in model. The result ofinstabilityindices is the convection was occured 1 hour before heavy rain. The result of vorticity is -0.25 × 10−3/s; 0.9 m/s in vertical velocity; and -0.5 × 10−3/s in divergence. From the study, it was also found that the process of cloud development has been seen for 30 minutes to 1 hour before the heavy rain.

Wave Disturbances and Their Role in the Maintenance, Structure, and Evolution of a Mesoscale Convection System

AbstractThis study investigates a nocturnal mesoscale convective system (MCS) observed during the Plains Elevated Convection At Night (PECAN) field campaign. A series of wavelike features were observed ahead of this MCS with extensive convective initiation (CI) taking place in the wake of one of these disturbances. Simulations with the WRF-ARW Model were utilized to understand the dynamics of these disturbances and their impact on the MCS. In these simulations, an “elevated bore” formed within an inversion layer aloft in response to the layer being lifted by air flowing up and over the cold pool. As the bore propagated ahead of the MCS, the lifting created an environment more conducive to deep convection allowing the MCS to discretely propagate due to CI in the bore’s wake. The Scorer parameter was somewhat favorable for trapping of this wave energy, although aspects of the environment evolved to be consistent with the expectations for an n = 2 mode deep tropospheric gravity wave. A bore within an inversion layer aloft is reminiscent of disturbances predicted by two-layer hydraulic theory, contrasting with recent studies that suggest bores are frequently initiated by the interaction between the flow within stable nocturnal boundary layer and convectively generated cold pools. Idealized simulations that expand upon this two-layer approach with orography and a well-mixed layer below the inversion suggest that elevated bores provide a possible mechanism for daytime squall lines to remove the capping inversion often found over the Great Plains, particularly in synoptically disturbed environments where vertical shear could create a favorable trapping of wave energy.

Experiments on lightning data assimilation: preliminary results

This article is devoted to the analysis of the first results of the impact of lightning data assimilation on the numerical weather forecast. The article includes a description of the used algorithm and the results of the conducted numerical experiments for the convective storms over Krasnodar region of Russia observed in 2017. Numerical weather prediction model WRF-ARW (Weather Research and Forecast) and lighting data gathered from WWLLN (Worldwide Lightning Location Network) are used [1. 2]. It was found that the average absolute errors of the temperature. atmospheric pressure. humidity. precipitation and wind are reduced. It is shown that the configuration of prognostic precipitation fields and their intensity is much closer to the observations. This is especially clearly seen for shallow precipitation (0-7 mm).

Simulation of seasonal dynamics of the global electric circuit diurnal variation

Based on the ionospheric potential (IP) parameterization, the seasonal dynamics of the diurnal variation of IP for 20162017 were modeled for the first time using the numerical weather forecast model WRF-ARW. The diurnal variation of the IP, averaged over the annual simulation periods, shows good agreement with the classical Carnegie curve. The proposed parametrization correctly reproduces the basic characteristics of the stationary global electric circuit generators. The annual variation does not show a precise repeatability from year to year, but in the winter season of the Northern Hemisphere a lower IP value was obtained, and in the summer - an increased one. The model diurnal variation demonstrates stable seasonal trends, and in the northern hemisphere, the variation is characterized by only one strongly distinguished maximum IP in the 16-18 UTC area of ~120% of the average value, while in the summer season the daily variation curve has two maxima with smaller value (~ 107% of average): morning at 89 UTC and evening at 1820 UTC. The model annual variation of the diurnal variation agrees with the experimental data of the surface field measuring in Antarctica in the period 20062011. The proposed parametrization and modeling technique made possible the accurate reproduction of the IP variation maximums times, their seasonal variability, and decreasing of the amplitude of variation in the summer period of the Northern Hemisphere.

Evaluating Forecast Skills of Moisture from Convective-Permitting WRF-ARW Model during 2017 North American Monsoon Season

This paper examines the ability of the Weather Research and Forecasting model forecast to simulate moisture and precipitation during the North American Monsoon GPS Hydrometeorological Network field campaign that took place in 2017. A convective-permitting model configuration performs daily weather forecast simulations for northwestern Mexico and southwestern United States. Model precipitable water vapor (PWV) exhibits wet biases greater than 0.5 mm at the initial forecast hour, and its diurnal cycle is out of phase with time, compared to observations. As a result, the model initiates and terminates precipitation earlier than the satellite and rain gauge measurements, underestimates the westward propagation of the convective systems, and exhibits relatively low forecast skills on the days where strong synoptic-scale forcing features are absent. Sensitivity analysis shows that model PWV in the domain is sensitive to changes in initial PWV at coastal sites, whereas the model precipitation and moisture flux convergence (QCONV) are sensitive to changes in initial PWV at the mountainous sites. Improving the initial physical states, such as PWV, potentially increases the forecast skills.

Numerical simulation of breeze circulation in Crimea using WRF-ARW model

Breeze circulation is an important atmospheric process that affects the weather and climate of coastal regions. Crimea is one of such regions. One of the methods of breeze research is numerical simulation, which has been quite successfully used to obtain information on breeze circulation in various geographical regions. The purpose of this work is to describe the regional features of sea breeze in Crimea, specifically, a breeze circulation near the Crimean Mountains. We use an array of satellite images and data of global operational analysis, NCEP GDAS, to choose a day with a pronounced breeze. A numerical experiment is performed for the day using a mesoscale model, WRF-ARW. Based on the results of the numerical simulation, the structure of the sea breeze circulation in Crimea is described. Some classical elements of the breeze characteristics of the flat part of Crimea are observed. A unique phenomenon of collision of breeze gravity currents has been revealed. It is a characteristic of the rather small land areas. Much attention is given to the features of breeze in the mountains associated with the complex topography.

Heterogeneous tide-surge interaction during co-occurrence of tropical and extratropical cyclones in the radial sand ridges of the southern Yellow Sea

The Radial Sand Ridges (RSRs) area in the southern Yellow Sea are subject to tropical and extratropical cyclone activities frequently, in which the special geometry feature and moving stationary tidal system result in complex storm-induced hydrodynamic processes, especially the tide-surge interactions. We studied a rare weather event influenced simultaneously by an extratropical cyclone EX1410 and Typhoon Vongfong as an example to investigate the characteristics of storm surges, wave-surge, and tide-surge interaction in the RSRs area, and applied a high-resolution integrally-coupled ADCIRC+SWAN model, in which the meteorological forcing inputs are simulated by the WRF-ARW model. The model is validated by records from 4 tide gauges and 2 wave buoys along the Yellow Sea coast. Results show that the tide-surge interactions are of considerable regional heterogeneousness. The surge curves at Lusi (in south RSRs) and Jianggang (in middle RSRs) have abrupt falls near the time of low tide, where the peak occurrence time of interaction residuals tend to shift towards the mid-ebb period. Significant increase of bed shear stress in shallow waters was proved the dominant factor to affect the tide-surge interaction in broad tidal flats of the RSRs area. Differently, the interaction pattern in the Xiyang Trough (in north RSRs), showed a unique rising in mid-flood period due to the phase advances of real surge waves in relatively deep waters. Therefore, we suggested to the local flood risk management that the tide-surge interaction tends to alleviate the flooding risk in the RSRs area around the time of high tide, but aggravate the risk on the rising tide in the Xiyang Trough and on the falling tide in large-scale tidal flats of the southern RSRs area.

The prediction of rainfall events using WRF (weather research and forecasting) model with ensemble technique

The research of ensemble technique has become popular in recent years, which can produce probabilistic predictions of rainfall on a short or medium scale. Prediction ensemble is a model formed by combining the predictive system model; the models used was member. This study aims to analyse the ability of the ensemble method in predicting rainfall events in Cilacap (07°45’ S, 109°02’ E) and Denpasar (08°37’ S, 115°13’ E). Data processing used ensemble equation; its ensemble member consisted of four members of running model WRF-ARW every cycle (00, 06, 12 and 18 UTC). In general, during the period of July 1 to 20 and February 1 to 20, 2016, the results of the models both single model and ensemble technique show that the model underestimate in predicting rainfall. Nevertheless, the single and three models of ensemble prediction methods estimated dry conditions very well but failed to predict the event of heavy rain. There were supported by the plot curve of the Relative Operating Characteristic (ROC) curve as a completely indicating that the three ensemble techniques performed the same results in all regions, none of them gave many different predictions between ensemble techniques and other ensemble techniques. The usual weighted or ensemble mean method produces almost identical rainfall predictions.

Development of Efficient Technique to Hindcast Typhoons and Associated Waves using Numerical Weather Model

Kim, G.H.; Jho, M.H., and Yoon, S.B., 2019. Development of efficient technique to hindcast typhoons and associated waves using numerical weather model. In: Lee, J.L.; Griffiths, T.; Lotan, A.; Suh, K-S, and Lee, J. (eds.), The 3rd International Water Safety Symposium. Journal of Coastal Research, Special Issue No. 91, pp. 41-45. Coconut Creek (Florida), ISSN 0749-0208.For the prevention of coastal inundations, numerical simulations of storm surges and waves based on the wind information of typhoons are indispensable. The wind field induced by typhoons were generally calculated using so-called parameter models. The parameter models are easy to use. However, it cannot take into account the interaction between the wind and the topographical terrain. In this study an efficient technique is developed to hindcast the wind fields for the past typhoon events. The WRF-ARW model is employed. The vortex components of wind field are first removed from the global data, and an artificial typhoon corresponding to the best-track data is obtained using the TC-bogus routine implemented in the WRF-ARW model, and is prescribed along with the typhoon track. The WRF-ARW run is conducted with the spectral nudging activated. In general, the wind field obtained in this way is much weaker than that of a real typhoon. Thus, an iterative technique is developed. The improved wind field obtained from the first WRF-ARW run is employed as an input wind field for the succeeding WRF-ARW run. The iteration is repeated until a satisfactory result is obtained. The calculated wind fields and associated wave fields are compared with the data measured at several buoy stations. Good agreement is achieved. The improved wind field can serve as a useful tool to simulate the coastal inundations for the design of coastal defense works.

Impacts of Different Physical Parameterization Configurations on Widespread Heavy Rain Forecast over the Northern Area of Vietnam in WRF-ARW Model

This study investigates the impacts of different physical parameterization schemes in the Weather Research and Forecasting model with the ARW dynamical core (WRF-ARW model) on the forecasts of heavy rainfall over the northern part of Vietnam (Bac Bo area). Various physical model configurations generated from different typical cumulus, shortwave radiation, and boundary layer and from simple to complex cloud microphysics schemes are examined and verified for the cases of extreme heavy rainfall during 2012–2016. It is found that the most skilled forecasts come from the Kain–Fritsch (KF) scheme. However, relating to the different causes of the heavy rainfall events, the forecast cycles using the Betts–Miller–Janjic (BMJ) scheme show better skills for tropical cyclones or slowly moving surface low-pressure system situations compared to KF scheme experiments. Most of the sensitivities to KF scheme experiments are related to boundary layer schemes. Both configurations using KF or BMJ schemes show that more complex cloud microphysics schemes can also improve the heavy rain forecast with the WRF-ARW model for the Bac Bo area of Vietnam.